/*******************************************************************************
 * Copyright (c) 2000, 2024 IBM Corporation and others.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.draw2d;

import java.beans.PropertyChangeListener;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;

import org.eclipse.draw2d.geometry.Dimension;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.draw2d.geometry.Rectangle;

/**
 * A scrolling Canvas that contains {@link Figure Figures} viewed through a
 * {@link Viewport}. Call {@link #setContents(IFigure)} to specify the root of
 * the tree of {@link Figure Figures} to be viewed through the {@link Viewport}.
 * <p>
 * Normal procedure for using a FigureCanvas:
 * <ol>
 * <li>Create a FigureCanvas.
 * <li>Create a Draw2d Figure and call {@link #setContents(IFigure)}. This
 * Figure will be the top-level Figure of the Draw2d application.
 * </ol>
 * <dl>
 * <dt><b>Required Styles (when using certain constructors):</b></dt>
 * <dd>V_SCROLL, H_SCROLL, NO_REDRAW_RESIZE</dd>
 * <dt><b>Optional Styles:</b></dt>
 * <dd>DOUBLE_BUFFERED, RIGHT_TO_LEFT, LEFT_TO_RIGHT, NO_BACKGROUND, BORDER</dd>
 * </dl>
 * <p>
 * Note: Only one of the styles RIGHT_TO_LEFT, LEFT_TO_RIGHT may be specified.
 * </p>
 */
public class FigureCanvas extends Canvas {

	private static final int ACCEPTED_STYLES = SWT.RIGHT_TO_LEFT | SWT.LEFT_TO_RIGHT | SWT.V_SCROLL | SWT.H_SCROLL
			| SWT.NO_BACKGROUND | SWT.NO_REDRAW_RESIZE | SWT.DOUBLE_BUFFERED | SWT.BORDER;

	/**
	 * The default styles are mixed in when certain constructors are used. This
	 * constant is a bitwise OR of the following SWT style constants:
	 * <UL>
	 * <LI>{@link SWT#NO_REDRAW_RESIZE}</LI>
	 * <LI>{@link SWT#NO_BACKGROUND}</LI>
	 * <LI>{@link SWT#V_SCROLL}</LI>
	 * <LI>{@link SWT#H_SCROLL}</LI>
	 * </UL>
	 */
	static final int DEFAULT_STYLES = SWT.NO_REDRAW_RESIZE | SWT.NO_BACKGROUND | SWT.V_SCROLL | SWT.H_SCROLL;

	private static final int REQUIRED_STYLES = SWT.NO_REDRAW_RESIZE | SWT.V_SCROLL | SWT.H_SCROLL;

	/** Never show scrollbar */
	public static int NEVER = 0;
	/** Automatically show scrollbar when needed */
	public static int AUTOMATIC = 1;
	/** Always show scrollbar */
	public static int ALWAYS = 2;

	private int vBarVisibility = AUTOMATIC;
	private int hBarVisibility = AUTOMATIC;
	private Viewport viewport;
	private Font font;
	private int hBarOffset;
	private int vBarOffset;

	private final PropertyChangeListener horizontalChangeListener = event -> {
		RangeModel model = getViewport().getHorizontalRangeModel();
		hBarOffset = Math.max(0, -model.getMinimum());
		getHorizontalBar().setValues(model.getValue() + hBarOffset, model.getMinimum() + hBarOffset,
				model.getMaximum() + hBarOffset, model.getExtent(), Math.max(1, model.getExtent() / 20),
				Math.max(1, model.getExtent() * 3 / 4));
	};

	private final PropertyChangeListener verticalChangeListener = event -> {
		RangeModel model = getViewport().getVerticalRangeModel();
		vBarOffset = Math.max(0, -model.getMinimum());
		getVerticalBar().setValues(model.getValue() + vBarOffset, model.getMinimum() + vBarOffset,
				model.getMaximum() + vBarOffset, model.getExtent(), Math.max(1, model.getExtent() / 20),
				Math.max(1, model.getExtent() * 3 / 4));
	};

	private final LightweightSystem lws;

	/**
	 * Creates a new FigureCanvas with the given parent and the
	 * {@link #DEFAULT_STYLES}.
	 *
	 * @param parent the parent
	 */
	public FigureCanvas(Composite parent) {
		this(parent, SWT.DOUBLE_BUFFERED, new LightweightSystem());
	}

	/**
	 * Constructor which applies the default styles plus any optional styles
	 * indicated.
	 *
	 * @param parent the parent composite
	 * @param style  see the class javadoc for optional styles
	 * @since 3.1
	 */
	public FigureCanvas(Composite parent, int style) {
		this(parent, style, new LightweightSystem());
	}

	/**
	 * Constructor which uses the given styles verbatim. Certain styles must be used
	 * with this class. Refer to the class javadoc for more details.
	 *
	 * @param style  see the class javadoc for <b>required</b> and optional styles
	 * @param parent the parent composite
	 * @since 3.4
	 */
	public FigureCanvas(int style, Composite parent) {
		this(style, parent, new LightweightSystem());
	}

	/**
	 * Constructs a new FigureCanvas with the given parent and LightweightSystem,
	 * using the {@link #DEFAULT_STYLES}.
	 *
	 * @param parent the parent
	 * @param lws    the LightweightSystem
	 */
	public FigureCanvas(Composite parent, LightweightSystem lws) {
		this(parent, SWT.DOUBLE_BUFFERED, lws);
	}

	/**
	 * Constructor taking a lightweight system and SWT style, which is used
	 * verbatim. Certain styles must be used with this class. Refer to the class
	 * javadoc for more details.
	 *
	 * @param style  see the class javadoc for <b>required</b> and optional styles
	 * @param parent the parent composite
	 * @param lws    the LightweightSystem
	 * @since 3.4
	 */
	public FigureCanvas(int style, Composite parent, LightweightSystem lws) {
		super(parent, checkStyle(style));
		getHorizontalBar().setVisible(false);
		getVerticalBar().setVisible(false);
		this.lws = lws;
		lws.setControl(this);
		hook();
	}

	/**
	 * Constructor
	 *
	 * @param parent the parent composite
	 * @param style  look at class javadoc for valid styles
	 * @param lws    the lightweight system
	 * @since 3.1
	 */
	public FigureCanvas(Composite parent, int style, LightweightSystem lws) {
		this(style | DEFAULT_STYLES, parent, lws);
	}

	private static int checkStyle(int style) {
		if ((style & REQUIRED_STYLES) != REQUIRED_STYLES) {
			throw new IllegalArgumentException("Required style missing on FigureCanvas"); //$NON-NLS-1$
		}
		if ((style & ~ACCEPTED_STYLES) != 0) {
			throw new IllegalArgumentException("Invalid style being set on FigureCanvas"); //$NON-NLS-1$
		}
		return style;
	}

	/**
	 * @see org.eclipse.swt.widgets.Composite#computeSize(int, int, boolean)
	 */
	@Override
	public org.eclipse.swt.graphics.Point computeSize(int wHint, int hHint, boolean changed) {
		// TODO Still doesn't handle scrollbar cases, such as when a constrained width
		// would require a horizontal scrollbar, and therefore additional height.
		int borderSize = computeTrim(0, 0, 0, 0).x * -2;
		if (wHint >= 0) {
			wHint = Math.max(0, wHint - borderSize);
		}
		if (hHint >= 0) {
			hHint = Math.max(0, hHint - borderSize);
		}
		Dimension size = getLightweightSystem().getRootFigure().getPreferredSize(wHint, hHint).getExpanded(borderSize,
				borderSize);
		size.union(new Dimension(wHint, hHint));
		return new org.eclipse.swt.graphics.Point(size.width, size.height);
	}

	/**
	 * @return the contents of the {@link Viewport}.
	 */
	public IFigure getContents() {
		return getViewport().getContents();
	}

	/**
	 * @see org.eclipse.swt.widgets.Control#getFont()
	 */
	@Override
	public Font getFont() {
		if (font == null) {
			font = super.getFont();
		}
		return font;
	}

	/**
	 * @return the horizontal scrollbar visibility.
	 */
	public int getHorizontalScrollBarVisibility() {
		return hBarVisibility;
	}

	/**
	 * @return the LightweightSystem
	 */
	public LightweightSystem getLightweightSystem() {
		return lws;
	}

	/**
	 * @return the vertical scrollbar visibility.
	 */
	public int getVerticalScrollBarVisibility() {
		return vBarVisibility;
	}

	/**
	 * Returns the Viewport. If it's <code>null</code>, a new one is created.
	 *
	 * @return the viewport
	 */
	public Viewport getViewport() {
		if (viewport == null) {
			setViewport(new Viewport(true));
		}
		return viewport;
	}

	/**
	 * Adds listeners for scrolling.
	 */
	private void hook() {
		getLightweightSystem().getUpdateManager().addUpdateListener(new UpdateListener() {
			@Override
			public void notifyPainting(Rectangle damage, java.util.Map<IFigure, Rectangle> dirtyRegions) {
				// nothing to do for now
			}

			@Override
			public void notifyValidating() {
				if (!isDisposed()) {
					layoutViewport();
				}
			}
		});

		getHorizontalBar().addSelectionListener(new SelectionAdapter() {
			@Override
			public void widgetSelected(SelectionEvent event) {
				scrollToX(getHorizontalBar().getSelection() - hBarOffset);
			}
		});

		getVerticalBar().addSelectionListener(new SelectionAdapter() {
			@Override
			public void widgetSelected(SelectionEvent event) {
				scrollToY(getVerticalBar().getSelection() - vBarOffset);
			}
		});
	}

	private void hookViewport() {
		getViewport().getHorizontalRangeModel().addPropertyChangeListener(horizontalChangeListener);
		getViewport().getVerticalRangeModel().addPropertyChangeListener(verticalChangeListener);
	}

	private void unhookViewport() {
		getViewport().getHorizontalRangeModel().removePropertyChangeListener(horizontalChangeListener);
		getViewport().getVerticalRangeModel().removePropertyChangeListener(verticalChangeListener);
	}

	private void layoutViewport() {
		ScrollPaneSolver.Result result;
		int vBarWidth = 0;
		int hBarHeight = 0;

		if ((getScrollbarsMode() & SWT.SCROLLBAR_OVERLAY) == 0) {
			org.eclipse.swt.graphics.Rectangle trim = computeTrim(0, 0, 0, 0);
			vBarWidth = trim.width;
			hBarHeight = trim.height;
		}

		result = ScrollPaneSolver.solve(new Rectangle(getBounds()).setLocation(0, 0), getViewport(),
				getHorizontalScrollBarVisibility(), getVerticalScrollBarVisibility(), vBarWidth, hBarHeight);
		getLightweightSystem().setIgnoreResize(true);
		try {
			if (getHorizontalBar().getVisible() != result.showH) {
				getHorizontalBar().setVisible(result.showH);
			}
			if (getVerticalBar().getVisible() != result.showV) {
				getVerticalBar().setVisible(result.showV);
			}
			Rectangle r = new Rectangle(result.viewportArea);
			r.setLocation(0, 0);
			getLightweightSystem().getRootFigure().setBounds(r);
		} finally {
			getLightweightSystem().setIgnoreResize(false);
		}
	}

	/**
	 * Scrolls in an animated way to the new x and y location.
	 *
	 * @param x the x coordinate to scroll to
	 * @param y the y coordinate to scroll to
	 */
	public void scrollSmoothTo(int x, int y) {
		// Ensure newHOffset and newVOffset are within the appropriate ranges
		x = verifyScrollBarOffset(getViewport().getHorizontalRangeModel(), x);
		y = verifyScrollBarOffset(getViewport().getVerticalRangeModel(), y);

		int oldX = getViewport().getViewLocation().x;
		int oldY = getViewport().getViewLocation().y;
		int dx = x - oldX;
		int dy = y - oldY;

		if (dx == 0 && dy == 0) {
			return; // Nothing to do.
		}

		Dimension viewingArea = getViewport().getClientArea().getSize();

		int minFrames = 3;
		int maxFrames = 6;
		if (dx == 0 || dy == 0) {
			minFrames = 6;
			maxFrames = 13;
		}
		int frames = (Math.abs(dx) + Math.abs(dy)) / 15;
		frames = Math.max(frames, minFrames);
		frames = Math.min(frames, maxFrames);

		int stepX = Math.min((dx / frames), (viewingArea.width / 3));
		int stepY = Math.min((dy / frames), (viewingArea.height / 3));

		for (int i = 1; i < frames; i++) {
			scrollTo(oldX + i * stepX, oldY + i * stepY);
			getViewport().getUpdateManager().performUpdate();
		}
		scrollTo(x, y);
	}

	/**
	 * Scrolls the contents to the new x and y location. If this scroll operation
	 * only consists of a vertical or horizontal scroll, a call will be made to
	 * {@link #scrollToY(int)} or {@link #scrollToX(int)}, respectively, to increase
	 * performance.
	 *
	 * @param x the x coordinate to scroll to
	 * @param y the y coordinate to scroll to
	 */
	public void scrollTo(int x, int y) {
		int hOffset = verifyScrollBarOffset(getViewport().getHorizontalRangeModel(), x);
		int vOffset = verifyScrollBarOffset(getViewport().getVerticalRangeModel(), y);
		performScroll(hOffset, vOffset);
	}

	/**
	 * Scrolls the contents horizontally so that they are offset by
	 * <code>hOffset</code>.
	 *
	 * @param hOffset the new horizontal offset
	 */
	public void scrollToX(int hOffset) {
		hOffset = verifyScrollBarOffset(getViewport().getHorizontalRangeModel(), hOffset);
		int hOffsetOld = getViewport().getViewLocation().x;
		if (hOffset == hOffsetOld) {
			return;
		}
		performScroll(hOffset, getViewport().getViewLocation().y);
	}

	/**
	 * Scrolls the contents vertically so that they are offset by
	 * <code>vOffset</code>.
	 *
	 * @param vOffset the new vertical offset
	 */
	public void scrollToY(int vOffset) {
		vOffset = verifyScrollBarOffset(getViewport().getVerticalRangeModel(), vOffset);
		int vOffsetOld = getViewport().getViewLocation().y;
		if (vOffset == vOffsetOld) {
			return;
		}
		performScroll(getViewport().getViewLocation().x, vOffset);
	}

	private void performScroll(int hOffset, int vOffset) {
		int dx = -hOffset + getViewport().getViewLocation().x;
		int dy = -vOffset + getViewport().getViewLocation().y;
		Rectangle clientArea = getViewport().getBounds().getShrinked(getViewport().getInsets());
		Rectangle blit = clientArea.getResized(-Math.abs(dx), -Math.abs(dy));
		Point dest = clientArea.getTopLeft();

		blit.width = Math.max(blit.width, 0);
		blit.height = Math.max(blit.height, 0);

		if (dx < 0) { // Moving left?
			blit.translate(-dx, 0); // Move blit area to the right
		} else { // Moving right
			dest.x += dx; // Move expose area to the right
		}

		if (dy < 0) { // Moving up?
			blit.translate(0, -dy); // Move blit area down
		} else { // Moving down
			dest.y += dy;
		}

		scrollChildren(dx, dy, blit, dest);

		getViewport().setIgnoreScroll(true);
		getViewport().setHorizontalLocation(hOffset);
		getViewport().setVerticalLocation(vOffset);
		getViewport().setIgnoreScroll(false);
		scrollRedraw(dx, dy, clientArea, blit);
	}

	private void scrollChildren(int dx, int dy, Rectangle blit, Point dest) {
		// fix for bug 41111
		Control[] children = getChildren();
		boolean[] manualMove = new boolean[children.length];
		for (int i = 0; i < children.length; i++) {
			org.eclipse.swt.graphics.Rectangle bounds = children[i].getBounds();
			manualMove[i] = blit.width <= 0 || bounds.x > blit.x + blit.width || bounds.y > blit.y + blit.height
					|| bounds.x + bounds.width < blit.x || bounds.y + bounds.height < blit.y;
		}
		scroll(dest.x, dest.y, blit.x, blit.y, blit.width, blit.height, true);
		for (int i = 0; i < children.length; i++) {
			if (children[i].isDisposed()) {
				continue;
			}
			org.eclipse.swt.graphics.Rectangle bounds = children[i].getBounds();
			if (manualMove[i]) {
				children[i].setBounds(bounds.x + dx, bounds.y + dy, bounds.width, bounds.height);
			}
		}
	}

	private void scrollRedraw(int dx, int dy, Rectangle clientArea, Rectangle blit) {
		Rectangle expose = clientArea.getCopy();
		if (dx != 0) {
			expose.width = Math.abs(dx);
			if (dx < 0) { // Moving left?
				expose.x += blit.width; // Move expose area right
			}
			redraw(expose.x, expose.y, expose.width, expose.height, true);
		}
		if (dy != 0) {
			expose.x = clientArea.x;
			expose.width = clientArea.width;
			expose.height = Math.abs(dy);
			if (dy < 0) { // Moving up?
				expose.y += blit.height; // Move expose area down
			}
			redraw(expose.x, expose.y, expose.width, expose.height, true);
		}
	}

	/**
	 * Sets the given border on the LightweightSystem's root figure.
	 *
	 * @param border The new border
	 */
	public void setBorder(Border border) {
		getLightweightSystem().getRootFigure().setBorder(border);
	}

	/**
	 * Sets the contents of the {@link Viewport}.
	 *
	 * @param figure the new contents
	 */
	public void setContents(IFigure figure) {
		getViewport().setContents(figure);
	}

	/**
	 * @see org.eclipse.swt.widgets.Control#setFont(org.eclipse.swt.graphics.Font)
	 */
	@Override
	public void setFont(Font font) {
		this.font = font;
		super.setFont(font);
	}

	/**
	 * Sets the horizontal scrollbar visibility. Possible values are
	 * {@link #AUTOMATIC}, {@link #ALWAYS}, and {@link #NEVER}.
	 *
	 * @param v the new visibility
	 */
	public void setHorizontalScrollBarVisibility(int v) {
		hBarVisibility = v;
	}

	/**
	 * Sets both the horizontal and vertical scrollbar visibility to the given
	 * value. Possible values are {@link #AUTOMATIC}, {@link #ALWAYS}, and
	 * {@link #NEVER}.
	 *
	 * @param both the new visibility
	 */
	public void setScrollBarVisibility(int both) {
		setHorizontalScrollBarVisibility(both);
		setVerticalScrollBarVisibility(both);
	}

	/**
	 * Sets the vertical scrollbar visibility. Possible values are
	 * {@link #AUTOMATIC}, {@link #ALWAYS}, and {@link #NEVER}.
	 *
	 * @param v the new visibility
	 */
	public void setVerticalScrollBarVisibility(int v) {
		vBarVisibility = v;
	}

	/**
	 * Sets the Viewport. The given Viewport must use "fake" scrolling. That is, it
	 * must be constructed using <code>new Viewport(true)</code>.
	 *
	 * @param vp the new viewport
	 */
	public void setViewport(Viewport vp) {
		if (viewport != null) {
			unhookViewport();
		}
		viewport = vp;
		lws.setContents(viewport);
		hookViewport();
	}

	private static int verifyScrollBarOffset(RangeModel model, int value) {
		value = Math.max(model.getMinimum(), value);
		return Math.min(model.getMaximum() - model.getExtent(), value);
	}

}
